wrote

Promaster Spectrum 7 50 mm lenses
... mount to the Nikon F10[sic]? I use to
have a Pentax K 1000 but it broke ...

If your Promaster lens went on your K1000 then it was
a 'K' mount lens and it will not fit a Nikon. 'Promaster'
is the name of a no-name line of lenses available in
various mounts: K, Minolta, Nikon ...

Probably not a good idea to get a Nikon FM-10 - it isn't
a Nikon but a budget-line Cosina (?) that is available
in several skins: K, Minolta, Nikon ...

Go to ebay (if you know what you are doing) or KEH (if
you would rather not take risks) and get an F3, probably
the best bang-for-buck in the used Nikon line-up. You can
usually save $50-$100 by buying one that the previous
owner had engraved. KEH's BGN bargain grade is often
equivalent to an ebay 'excellent'.

For a budget lens the 50mm f1.8 'E' is recommended.

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index.htm
n o lindan at ix dot netcom dot com